Apparatus for casting thixotropic material



United States Patent 3,111,058 APPARATUS FUR CASTENG THEXGTROPICMATERIAL Herschel Q. Holley and Erwin Marsh, Marshall, Tex.,

assignors to 'lliiolrol llmi3l Corp, Trenton, N.J., a

corporation of Delaware Filed June 26, 1959, Ser. No. 823,153 11 laims.(Cl. 86--20) The present invention relates to apparatus for producingflow of thixotropic material, and more particularly to casting solidfuel propellants in the casings of rocket engines. The term thixotropicmaterial as used in the specification and claims is intended to includethose viscous materials in which the rate of flow can be increased bymechanical treatment as well as those materials which can only be madeto flow by mechanical treatment.

Solid fuel propellants used in rocket engines have a thick dough-likeconsistency which sets-up into a substantially rigid mass. lt is theusual practice to cast the material to form a particular shape bypouring the material into a mold or directly into the casings of therocket engines. Such solid fuels are usually mixed in batches anddelivered from a mixer to a casting can for intermediate storage or fordirect use in a casting apparatus. When the material is to be cast, acasting can is mounted on the casting apparatus from which the materialis poured into a mold. The material is rendered fluent by theapplication of heat and pressure, but the casting of the material hasalways presented a problem because of its resistence to flow. Recentlydeveloped types of solid fuel propellants have further accentuated theproblem because they are so viscous that they will not readily flow bythe application of heat and pressure within the limits which can besafely used in production.

One of the objects of the present invention is to provide an apparatusfor improving the flow characteristics of thixotropic materials to andfrom containers to facilita-te casting the materials in molds.

Another object is to provide an apparatus for casting thixotropicmaterial of the type indicated which subject the entire mass of materialto mechanical treatment for enhancing flow from a casting can and into amold.

Another object is to provide a casting can which renders thixotropicmaterial fluent when vibrated and acts as a pump for propelling thematerial through a feed line.

Still another object is to provide a casting can which is of arelatively simple and compact construction, economical to manufactureand reliable in its operation to render the thixotropic material fluent.

These and other objects will become more apparent from the followingdescription and drawing in which like reference characters denote likeparts throughout the several views. It is to be expressly understood,however, that the drawing is for the purpose of illustration only and isnot a definition of the limits of the invention, reference being bad forthis purpose to the appended claims.

In the drawing:

FIGURE 1 is a side elevational view showing the thixotropic materialbeing dumped from a mixer into a casting can;

FIGURE 2 is a sectional view of a casting apparatus in side elevationand showing the vibrating platform on which the casting can is mounted;

FIGURE 3 is a top plan view of a casting can showing the fin platesattached to the sides of the can and extending inwardly toward thecenter thereof;

FIGURE 4 is a sectional view taken on line 4-4 of FIGURE 3 and showingthe tin plates attached to the side of the can through only a portion oftheir length adjacent the top and extending inwardly and downwardlytoward the center and bottom of the can;

ii i lfi-Sd Patented Nov. 19,1963

FIGURE 5 is a perspective view of the open top of the can and showingthe dough-like consistency of the thixotropic material delivered to acan; and

FIGURE 6 is a view similar to FIGURE 5 showing the fluid consistency ofthe material after treatment in the apparatus of the present invention.

In an endeavor to develop a way of casting certain types of solid fuelpropellants which would not flow by the methods of casting previouslyused, it was discovered that the material would become fluid, at leastto some degree, when vibrated. However, a conventional vibrating devicewhen attached to the side of a casting can did not render the materialfluent as the vibrations were absorbed by the material within two orthree inches of the external wall of the can. The casting can was thenmounted on a vibrating device of sufficient size to bodily vibrate thecm and material. This vibration also was found to be ineffective tocause the material to flow to the degree required for casting. It wasthen discovered that bailles or fin plates attached to the inside of thecan and extending inwardly into the interior of the mass were effectiveto cause the material to flow until the level of the material in the canfell below the fin plates at which time the flow again became slow. Thebafiles were then extended throughout the height of the can and only theupper portion of the battle fins attached to the sides of the can.Baille plates of this type were found to be very effective in producingflow when the entire can and contents was vibrated and the tin platesacted as propellers for pushing the thixotropic material through thefeed line in the manner of the pump. Also, it was found that theapparatus was very useful in improving the flow characteristics anddecreasing the time required for casting less viscous types of solidfuel propellants.

Referring to the drawings, a batch of the thixotropic material, such asa liquid polymer used as a rocket fuel, is processed in a mixer 10 shownin FIGURE 1. After a batch of the material has been processed, the mixer10 is tilted to dump the dough-like mass of material into the open topof a casting can 11. The material falls into the can 11 in separatedmasses or chunks and takes a form 'n the can generally like thatillustrated in FIGURE 5. referably, the casting can 11 is mechanicallyvibrated while the material is being delivered to the can from mixer 19to cause the material to flow into and fill the can, as illustrated inFIGURE 6. To this end, the casting can may be mounted on the vibratingtable of the casting apparatus 12, later to be described, during afilling operation, or may be mounted on a separate but similar vibratingapparatus during filling. Thus, the thixotropic material may bedelivered alternately from the mixer 10' to casting can 11 and from thecasting can to a mold M while mounted on the casting apparatus 12, orthe material may be placed in a can at the mixer for temporary storageor for transfer to a casting apparatus located remotely from the mixerIt).

In accordance with the present invention, the casting can 11 has finplates 13 projecting inwardly from the side walls 14 toward the centerand downwardly toward the bottom wall 15 of the can. Casting can 11 mayhave any desired shape and any required number of fin plates 13projecting inwardly from its side walls 14. In the illustratedembodiment the casting can 11 is of generally cylindrical shape, seeFIGURES 3 and 4, having a vertical side wall 14, a curved bottom wall 15with an axial outlet opening 16 and an open top 17. An outer jacket wall18 surrounds the inner wall 14 to provide a space 19 therebetweenthrough which a heating medium is circu lated to heat the thixotropicmaterial in the can. As illustrated in FIGURE 4, a nipple 20 dependsfrom the outlet opening 16 in bottom wall 15. Nipples 21 and 22 also areprovided at the side of the outer jacket wall 18 and have fittings 23and 24 for detachable connection to conduits for conducting a heatingmedium, such as hot water, into a jacketed space The open top 17 of thecasting can Ill is adapted to be closed and sealed by a cover 25; seeFIGURE 2, which is held on the can by clamps 2.5. Cover 25 has a nipple2'7 projecting therefrom and a fitting 28 for connection to a line forsupplying a fluid under pressure, such as air, to the closed castingcan. Casting can 11 is mounted on legs 29 which depend from the skirt 34welded or otherwise attached to the outer wall 18.

Pin plates 13 transmit motion from the walls of the casting can ll tothe interior of the mass of thixotropic material therein andmechanically work the material in shear transverse to the direction offlow. While the fin plates 13 may take other forms, the particularconstruction illustrated in this construction, four of the tin plates 13are provided and are of generally rectangular form and positionedvertically in the casting can with the upper edges below the top or" thecan and the outer edges adjacent the side wall 14- of the can. The upperportions 36 of the outer edges project laterally beyond the lower edgeportions 31 for a distance of from one third to one half the height ofthe fin plates, for example, to 6 inches, and the laterally projectingportions 36 are attached to the wall as by weldin The lower edge portion31 of each fin plate 13 is off-set inwardly from the side wall 14, butpositioned closely adjacent thereto, and the lower edge 32 overlies thebottom wall in closely adjacent relationship. For example, the side andbottom edges 31 and 32 of the fin plates 13 may be spaced from the sidewall 14 and bottom 15 about one-quarter of an inch. The rectangular finplates 13 project radially inwardly from the cylindrical wall 14 withthe inner edges 33 adjacent the axis of the casting can 11 and closelyadjacent each other. Thus, each of the fin plates 13 is attached tocasting can 11 at the upper portion 39 of its outer edge only and isfree to vibrate transversely in the casting can H and mechanically workthe thixotropic material therein.

When the thixotropic material is to be cast a casting can 11 with thematerial therein is mounted on a vibrating platform 35 of the castingapparatus 12. To this end, feet 3d at the lower ends of the legs 29 areclamped to pads 37 on the platform 35 by means of clamps or bolts 38, asshown in FIGURE 2. The platform 35 may be vibrated by any suitablemechanism, but the one illustrated in FIGURE 2 has been found to beespecially effective. The vibrating mechanism illustrated comprises acircular base 4-0 and a plurality of springs 41 positioned between thebase and platform 35 in equally s aced relation around the periphery ofthe base. Springs 41 extend at an angle to the vertical, for example, 45and the ends of the springs bear against angular abutments 42 and 43 onthe base and platform, respectively. A link 44 for each spring 41extends between the base it? and platform 35 and across the spring at anangle equal and opposite the angle of the spring 41. The ends 45 and 4-6of each link 4-4 are pivotally connected to the base and platform 35,respectively. Base 4% is anchored to the floor by bolts 39 and theplatform 35 is mounted on the anchored base for a combined verticalreciprocation and lateral oscillation.

Vibrating platform 35 is excited by a shaft 47 mounted in bearings 43and 49 on the base .0 and driven'by a pulley 5i? and driving belt 51.Eccentrics 52 and 53 on said shaft 47 operate in eccentric straps 54 and55 having their upper ends pivotally connected to lugs 56 and 57depending from the opposite sides of the table 35 through pins 59.Angularly extending links 69 are pivotally connected between the pin 59and the base 49 to control the motion of the platform 35 from theeccentrics 52 and 53. The shaft and eccentrics 52 and mounted thereonare rotated at a speed to produce a combined vertical reciprocating andlateral oscillating vibratory motion having a frequency corresponding tothe natural frequency of the weight loaded springs 41. In a particularapplication, a casting can ill of 20 gallons capacity is used and thetotal load to be vibrated is 1092 pounds of which 810 pounds is thecasting can lll filled with propellant. The springs are so designed asto produce a natural frequency of 385 cycles per minute for thisparticular spring load. Thus, the shaft is initially rotated at 385 rpm.and the speed is gradually increased as the load decreases to maintainthe vibration at the natural frequency of the spring-load. Thisvibration of platform 35 and casting can 511 is transmitted by the finplates 13 to the thixotropic material in the can and mechanically workthe material which renders it fluid.

he thixotropic material flows from the elevated casting can 11 to mold Mthrough a delivery conduit 61. Delivery conduit 61 in the illustratedembodiment is in the form of a flexible hose having its upper endattached to the nipple 28 depending from the casting can 11 by of a hoseclamp s2. Hose 61 extends downwardly from the nipple 29 and thenlaterally between the legs 29 with its lower end overlying the mold M tobe filled. A suitable elongated nozzle 63 may be used, which detachablyconnects to the lower end of hose 61, to reach down into the mold anddeliver the material close to the bottom and adapt the nozzle to beraised as the level of the material rises in the mold. When required,additional vibrating devices 65' are provided at spaced positions alongthe hose 61 which will produce vibrations in a direction transverse tothe direction of flow of the thixotropic material therethrough. A flexvalve also may be provided for controlling flow through hose 61 andcomprises opposed clamping elements 66 and 6'7 for pinching a portion ofthe flexible hose therebetween.

As shown in FlGURE 2, mold M is mounted in chocks 6 3 on a platform 6%also mounted on springs 70 for vibration to cause the thixotropicmaterial to flow into and completely fill the mold. Platform 69 may bevibrated by a mechanism like that used for vibrating the casting can 11or by other suitable vibrating mechanism. ()ne form of the inventionhaving now been described, the mode of operation of the apparatus tocast the thixotropic material is now described.

A batch of the thixotropic material in the form of a liquid polymer isdischarged from mixer 10 into the open top of casing can 11. The castingcan 11 may or may not be vibrated during a filling operation and ifvibrated it may be mounted on the vibrating platform 35 of the castingapparatus 12., or may be vibrated by a separate vibrating mechanism. Forpurposes of description let it be presumed that the casting can ismounted on the casting apparatus 12 while the can 11 is being filled.During the filling operation, the clamping elements 66 and 67 of theflex valve are actuated to pinch the flexible delivery conduit 61 toprevent flow therethrough. If the casting can 11 is not vibrated duringa filling operation the material will have a consistency like thatillustrated in FIGURE 5. Preferably, the casting can 11 is vibratedduring a filling operation and the material flows into the can asillustrated in FIGURE 6.

After the casting can 11 has been filled, cover 25 is applied to theopen top 17 and sealed thereto by the clamps 26. Lines are then attachedto the fittings 23 and 24 on can 11 to deliver hot water to the jacketedspace 19 to maintain the material in the can at a desired temperatureof, for example, F. A fluid pressure line also is connected to thefitting 28 in the cover 25 to apply pressure to the top of thethixotropic material in the can 11.

To pour a casting, the clamps 66 and 67 of the flex valve are releasedand the platform 35 of the casting apparatus is vibrated by rotatingshaft 47. Eccentrics 52 and 53 on shaft 45 acting through the links 54and 55 produce a combined reciprocation and oscillation of the platformat the natural frequency of the mounting springs 41. Casting can Illvibrates bodily with the platform and the vibration is transmitted bythe fin plates 13 from the Wall 14 of the can into the interior of thethixotropic material therein. Due to the connection of the fin plates 13through a short length of the upper portion 30 of the side edges only,the fin plates vibrate independently of the can and work the materialwhich transforms it from a thick dough-like mass as illustrated inFIGURE 5 to a fluid which fills the can at a fixed liquid level asillustrated in FIGURE 6. In addition, the vibrating fin plates 13 act topropel the now fluent material through the outlet opening 16' in thebottom of the can. The fluent material then flows downwardly through thedelivery conduit 61 and nozzle 63 into the bottom of the mold M. Theadditional vibration produced by the vibrating rings as on the hose andthe platform 69 supporting the mold M insures the continuous flow of thematerial to completely fill the mold. As the level of the material risesin the mold M, the nozzle 63 may be raised to maintain the outlet end ofthe nozzle adjacent the surface of the material to prevent entrapment ofair therein.

When the pouring of a casting has been completed, the clamping elements66 and 67 of the flex valve are actuated to pinch the flexible deliveryconduit and stop the flow. The mold M with the material therein is thenremoved from the platform 69, a new mold mounted in the chocks 68, theclamping elements 66 and 67 of the flex valve withdrawn and the pouringin the new mold initiated. When all of the material in the casting can11 has been poured, the rotation of the shaft 47 is stopped, the cover25 removed from the casting can 11 and another batch of material isdelivered to the can through its open top 17, preferably while vibratedby the platform 35 of the casting apparatus.

It will be understood that the material to be cast may be delivered fromthe mixer into a casting can 11 either with or Without vibration andtemporarily stored, or the filled casting can may be used to transportthe material from the mixer 10 to a remotely located casting apparatus12.. When the latter is the case, the casting can llll is mounted on theplatform 35 of the casting apparatus 12 and connected thereto by thefastening means 38.

In one application where the polymer containing an oxidizer andadditives had a consistency almost like wet sand and would not flow whenheated to 138 F. with an applied pressure of 30 pounds per square inch,the material was rendered fluent enough in the apparatus of the presentinvention to cast 215 pounds of the material in 15.5 minutes. When thevibration was stopped the material could not be cast. Various othercompositions of liquid polymers used as solid fuel propellants weretested and the flow characteristics of all of the compositions weregreatly improved by use of the apparatus of the present invention aswell as producing an improvement in the casting.

It will now be observed that the present invention provides an apparatusfor rendering thixotropic material fluent for flow into and fromcontainers to adapt the material to be cast. It also will be observedthat the present invention provides an apparatus for casting thixotropicmaterial which affects the entire mass of material to cause it to flowfrom a casting can and fill the mold into which it is poured. It willfurther be observed that the present invention provides a casting canwhich renders the thixotropic material fluid when vibrated and acts as apump for propelling the material through a delivery conduit. It willstill further be observed that the present invention provides a castingcan of the type indicated which is of relatively simple and compactconstruction, reliable in rendering the thixotropic material fluid, andis economical to manufacture.

While a single embodiment of the invention is herein illustrated anddescribed, it will be understood that changes may be made in theconstruction and arrangement of elements without departing from thespirit or scope of the invention. Therefore, Without limitation in thisrespect the invention is defined by the following claims.

We claim:

1. Apparatus for casting thixotropic material comprising a mold to befilled, a vibrating platform, a container for the thixotropic materialhaving an outlet opening and rigidly mounted on the vibrating platform,a conduit from the outlet opening in the container to the mold, meansfor vibrating the platform and container mounted thereon, and fin platesprojecting inwardly from the wall of the container to transmitvibrations from the wall into the interior of the thixotropic materialtherein whereby to render the thixotropic material in the containerfluid.

2. Apparatus for casting liquid polymers having a thick Viscousconsistency comprising a mold to be filled, a vibrating platform, acontainer for the polymer having an outlet opening and rigidly mountedon the vibrating platform, a conduit from the outlet opening in thecontainer to the mold, means for vibrating the platform and containermounted thereon, and fin plates projecting inwardly from the wall of thecontainer to transmit vibration from the wall into the interior of thepolymer therein whereby to render the polymer in the container fluid.

3. Apparatus for casting a thixotropic propellant material into thecasing of a rocket engine comprising the rocket engine casing, a castingcan containing the thixotropic material and having an outlet opening inthe bottom, a platform on which the casting can is mounted, a conduitextending from the outlet opening in the casting can to the casing ofthe rocket engine to be filled, means for vibrating the platform andcasting can mounted thereon about a vertical axis through the castingcan, and fin plates projecting inwardly from the sides of the castingcan into the interior of the thixotropic material and having edgesterminating adjacent each other at the interior of the material torender it fluent and cause it to flow from the casting can into theconduit.

4. Apparatus for casting thixotropic propellant material in accordancewith claim 3 in which the upper portions of the outer edges of the finplates are attached to the sides of the casting can, the fin platesextending radially inwardly with the inner edgm closely adjacent eachother, and the free portions of the fin plates below the attached edgesextending downwardly closely adjacent the sides and bottom of thecasting can and acting as vibrating paddles.

5. Apparatus for casting a thixotropic propellant material in accordancewith claim 3 in which the casting can has an inner wall to which the finplates are attached, a jacket wall surrounding the inner wall to providea space therebetween, and inlet and outlet connections to the jacketwall for circulating a fluid heating medium in the space between thewalls.

6. Apparatus for casting a thixotropic propellant material in accordancewith claim 3 in which a cover is provided for closing the open top ofthe casting can, means for clamping the cover to the casting can toprovide a pressure vessel, and a fitting on the cover for supplyingfluid thereto under pressure.

7. Apparatus for casting a thixotr-opic propellant material inaccordance with claim 3 in which vibrating means are mounted on theconduit extending from the outlet opening of the casting can to thecasing to be filled for vibrating the conduit to insure flow of thethixotropic material therethrough.

8. Apparatus for casting a thixotropic propellant material in accordancewith claim 3 in which the means for vibrating the platform comprises abase, springs extending between the base and platform at an angle to theplanes thereof, links extending between the base and platform at anangle opposite to the angle of the springs, the ends of the links beingpivotally connected to the base and platform, respectively, eccentricmeans mounted on the base and connected to vibrate the platform, andmeans for driving the eccentric means at the natural frequency of thesprings to vibrate the platform with a combined oscillating andreciprocating motion.

9. A container for thixotropic material which may be bodily vibrated torender the material fluent for ilow into or from the container, saidcontainer being cylindrical and having a longitudinal axis and enclosingwa ls including a side Wall parallel to the longitudinal axis and abottom Wall transverse thereto with an outlet opening at the axis,vibrating fin plates having a portion of their side edges only attachedto the side Wall of the container and extending inwardly toward thecenter of the container with their inner edges adjacent each other andthe outlet opening, and the unattached edges of the free portions ofsaid fin plates adjacent the side and bottom Walls of the containerbeing positioned closely adjacent thereto for relative movement.

10. A container for thixotropic material in accordance with claim 9having an open top, a cover for closing the open top of the container,means for clamping the cover to the container to provide a pressurevessel, and a connection on the cover for supplying fluid under pressureto the top of the closed pressure vessel.

11. A container for thixotropic material in accordance UNITED STATESPATENTS 988,798 Maxim Apr. 4, 1911 988,886 Maxim Apr. 4, 1911 1,835,937Ellis Dec. 8, 1931 2,156,541 Misenhirner et a1 May 2, 1939 2,414,273Richman Jan. 14, 1947 2,426,619 Knight Sept. 2, 1947 2,435,610 SchneiderFeb. 10, 1948 2,956,711 Mortara et a1. Oct. 18, 1960 3,004,462 Cook eta1. Oct. 17, 1961 FORElGN PATENTS 126,427 Great Britain May 15, 1919

1. APPARATUS FOR CASTING THIXOTROPIC MATERIAL COMPRISING A MOLD TO BEFILLED, A VIBRATING PLATFORM, A CONTAINER FOR THE THIXOTROPIC MATERIALHAVING AN OUTLET OPENING AND RIGIDLY MOUNTED ON THE VIBRATING PLATFORM,A CONDUIT FROM THE OUTLET OPENING IN THE CONTAINER TO THE MOLD, MEANSFOR VIBRATING THE PLATFORM AND CONTAINER MOUNTED THEREON, AND FIN PLATESPROJECTING INWARDLY FROM THE WALL OF THE CONTAINER TO TRANSMITVIBRATIONS FROM THE WALL INTO THE INTERIOR OF THE THIXOTROPIC MATERIALTHEREIN